1. Field of the Invention
The field of the invention is new pyrethroids useful for control of pests.
2. The Prior Art
Pyrethrin-like compounds (pyrethroids) are known in the chemical art. Many such compounds have been shown to possess insecticidal properties, but most have failed to provide entirely satisfactory insect and/or acarina control. None, to the best of our knowledge, has been suggested for the control of soil-borne insects and, with few exceptions, all have been subject to extremely rapid degradation to non-toxic substances. This latter property has been recognized in the past as a major deficiency of the pyrethroids. While such compounds have provided excellent knockdown of insects, rapid degradation of said compounds has resulted in lack of residual insect control even for a few days.
In this regard, it is well-known that pyrethrins and synthetic pyrethroids are generally too unstable to air and light to be useful for the control of agronomic and forest insects [Y. L. Chen and J. E. Casida, J. Agr. Food Chem., 17, 208(1969)]. Although this rapid degradation may be desirable for environmental reasons, it is of course obvious that there must be sufficient residual presence of the toxicant to ensure economic control of a particular pest.
To this end, a great deal of effort has been expended in attempting to effect sufficient stabilization of existing materials, through the use of light absorbers and antioxidants, to allow their useful application, e.g. see R. P. Miskus and J. S. Andrews, J. Agr. Food Chem., 20, 313(1972).
Another approach to the development of highly active effective pyrethroid insecticides has involved a search for molecular types which retain a high degree of insecticidal activity typical of the best pyrethroids while introducing sufficient stability to air and light to ensure their applicability in the field. An apparent success in this effort is the recent discovery by Elliott and coworkers of the compound m-phenoxybenzyl (.+-.) -cis, trans-2,2-dimethyl-3(2,2-dichlorovinyl)cyclopropane carboxylate [M. Elliott et al., Nature 246, 169(1973)]. The improved stability of this compound (permethrin) has resulted in part from the replacement of the oxidatively susceptible dimethylvinyl side-chain on the cyclopropane ring of chrysanthemic acid by a dichlorovinyl substituent. Such an improvement might indeed have been anticipated based on Chen and Casida's earlier work. However, the fortuitous combination of improved stability and high degree of insecticidal activity found by Elliott was unexpected.
We have now discovered a new series of esters which, in addition to showing an amazing degree of insecticidal activity, are unexpectedly stable on plant surfaces. This sought for but most difficult to find combination of activity and stability result from novel esters of the type described herein.
Unlike permethrin, these compounds do not rely on replacement of essential methyl groups by chlorine atoms to effect greater stability. Indeed, no atoms other than carbon, hydrogen, and oxygen are present. Thus it is surprising that the esters of this invention are not susceptible to the immediate light-promoted oxidative degradation which limits the agronomic effectiveness of most of the pyrethroids disclosed to date.
It is, therefore, an object of the present invention to provide pyrethroid compounds which are highly effective insecticidal compounds and which are not subject to immediate degradation, but provide insect control for from several days to several weeks before they are detoxified.
It is also an object of this invention to provide pyrethroid compounds which are useful as contact and/or stomach poisons effective for protecting important agronomic crops, such as cotton, soybeans, tobacco, alfalfa, corn, cole crops, leafy vegetables, snapbeans and tomatoes, from attack by insects, particularly Lepidopterous, Homopterous and Colepterous insects.
The importance of these insects is evidenced by the fact that in 1973 the cotton boll weevil, Anthonomus grandis (Boheman) and the tobacco budworm, Heliothis virescens (Fabricius) were two species important among the cotton insect complex which required control measures involving 45 million treatment acres. For soybeans and snapbeans, sprays were made to control a complex of insects which included the Mexican bean beetle, Epilachna varivestis Mulsant and the black bean aphid, Aphis fabae (Scopoli) involving over 5 million treatment acres; and the cabbage looper, Trichoplusia ni (Huber) was a major member of an insect complex which attacked sweet corn, cole crops, leafy vegetables and tomatoes and required insecticide treatment of an additional 8 million acres of crops.
While many pyrethroids exhibit some insecticidal properties there are, nevertheless, many insects such as those mentioned above which are not adequately controlled by the pyrethroids presently available. Advantageously, the compounds of the present invention are insecticidal and, more importantly they are pyrethroids which are effective for the control of the above indicated boll weevil, budworm, Mexican bean beetle, aphid and cabbage looper, complex, which ravage cotton, tobacco, soybeans, alfalfa, corn, cole crops, leafy vegetables, snapbeans and tomatoes.
It is a further object of this invention to provide pyrethroids which are highly effective soil insecticidal agents.
It is also an object of this invention to provide pyrethroids which are highly effective topical insecticidal and acaricidal agents useful for the treatment of warmblooded or homothermic animals.
U.S. Pat. Nos. 3,835,176, issued Sept. 10, 1974 and 3,823,177, issued July 9, 1974. The U.S. Pat. No. 3,835,176 to Matsuo et al. discloses alpha-cyanobenzyl cyclopropanecarboxylates as insecticidal agents. These compounds are effective as stated; however, they are not said to be useful for control of soil insects or exhibit extended residual insecticidal activity. The U.S. Pat. No. 3,823,177 to Fanta et al. relates to insecticidal esters of spirocarboxylic acids. However, like the U.S. Pat. No. 3,835,176, Fanta et al. do not suggest soil insecticidal activity, or extended residual activity.